Weather Blog: Winter forecast 2013-2014

Thank you for reading the Weather Watch 12 blog! One word, 89 days -- winter. In today's blog we breakdown the much anticipated winter forecast for southeastern Wisconsin. Included is the method we use to create the forecast, the reasoning behind our forecast, and finally how much snow and cold you can expect.

Since weather records began in the 1800s, Milwaukee has seen snow in 9 different months -- as early as September 20 and as late as May 31. The first measurable snow this season blanketed a pumpkin patch in Caledonia on November 11.

The bulk of our average annual snowfall of 46.9" in Milwaukee piles up from December-March. Here's a monthly breakdown of average snowfall per month. Both October, April, and May average small amounts.

November 2.4"

December 10.6"

January 14.7"

February 9.8"

March 7.0"

Last winter Weather Watch 12 predicted 36" to 48" of snow for Milwaukee. The final total was 45.0". Our temperature forecast of near average with big temperature swings was spot on. The final departure from average for December-March finished at +0.6 degrees.

The challenge of predicting an entire season is one we take head on using a weather pattern theory called Lezak's Recurring Cycle or the LRC.

Here are the basics of the theory

A unique weather pattern sets up every year between the start of fall and mid-November.

Long term long-wave troughs(low pressure) and ridges(high pressure) become established. These dominant repeating features are clues to where storm systems will reach peak strength, and where they will be their weakest.

Once the weather pattern is set it cycles, repeats, and continues through winter, spring and into summer. Identifying the cycle length helps tremendously when making long range weather predictions.

The LRC is a 10-11 month pattern! It isn't just one long-wave trough, storm system, or ridge. Instead, a sequence of troughs and ridges that are cycling around the Northern Hemisphere.

The key to using the LRC with success is knowing the cycle duration. The cycle duration this LRC season is around 57-58 days as discussed in the blog on October 30. You can read that discussion by clicking here.

After weeks of analysis here are the features of the cycling weather pattern that will drive our weather this winter.

Feature #1 - Active Periods

We have identified several periods or storm systems that should provide our area with the bulk of its precipitation.

The first timeframe we noted was between October 2-17. This two week window produced 2.61" of rainfall in Milwaukee. As this part of the pattern repeats it should provide several chances for precipitation. The return timeframe would be early to mid-December and again in late January to roughly the first 10 days of February.

Another active part of the pattern occurred with a storm system around Halloween. Over 1" of precipitation was measured in Milwaukee. The 500mb(middle of the atmosphere) map below shows a trough or area of low pressure over the Plains and Midwest. This feature should return again toward the end of December.

A final feature of this pattern's active periods is the most recent storm system that brought severe weather, heavy rain, and gusty winds to the Midwest. This feature has strong upper level winds associated with it, and tracks in a position that may lead to a powerful winter storm in future cycle(s).

While we typically think snow in the winter, the active periods will likely have the potential to produce all precipitation types.

Feature #2 - Cold/Drier Periods

What would winter be without arctic airmasses sending temperatures into the deep freeze. While we will see several shots of bitter cold this winter, one timeframe stands out. October 18-29 delivered an extended period of below average temperatures. This part of the pattern featured a predominately northwest flow aloft, a series of clipper systems, and shots of early season cold.

Translating this into winter when this feature repeats, light precipitation and overall colder than average temperatures are expected. The image below is from October 23. Notice the deep trough over the Great Lakes(cold) and the ridge over the West(warm).

Clearly there are other parts of the pattern that will unlock frigid airmasses, but this timeframe looks to be the one with the greatest potential to linger more than a few days.

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Winter Forecast

Temperatures = Near Average

Discussion: The cold periods this winter will get your attention. The coldest parts of the pattern have the potential to drop temperatures well below zero. For the first time in 5 years Milwaukee may see at least one night with temperatures around -10! It's not all cold though, in fact the southwest flow part of the pattern, while active, should allow us to thaw out and jump above average. The ups and downs should again keep temperatures overall close to average.

Snowfall = 42 to 54 inches

Discussion: Precipitation totals look to finish near to above average this winter season. However, I think we battle precipitation type with some of our active stretches of weather meaning potentially rain/mix to snow. Any rain or mix cuts down on snow totals. The forecast position of the main storm track should keep the heaviest winter snow totals to the west-northwest of Milwaukee. Areas from Green Bay to Wausau to the Twin Cities and even around Madison should see above average snowfall this winter.

For southeastern Wisconsin including Milwaukee, there is an increased chance of 1-2 'big' snows this winter. This is based on features we highlighted in the active period that will support stronger storm systems.

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As we gain confidence in the pattern we will begin to issue monthly outlooks highlighting weather events that we are expecting weeks to a month in advance. Stay with Weather Watch 12 this winter season for your most accurate day-to-day and long range forecasts.

For the latest weather information watch WISN 12 News, and for updates throughout the day follow me on Twitter @jnelsonweather

Have a great day!

Jeremy Nelson

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